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Posts Tagged ‘ESXi’

Time settings/issues on ESXi 4.1

December 16, 2010 Leave a comment

Here are some short and sweet items that i discovered yesterday;

Interestingly, ESXi does not allow you to change the timezone, it is permanently set to UTC.

Also, If you setup an NTP server on your ESXi hosts and that NTP server goes away for some reason, the ESXi host will not revert to using its’ own clock or even continuing to make a valient effort of keeping time, it instead reverts to January 1, 0001, to say this creates some issues is simplifying it.  The ESX hosts complain about not being able to “synchronize”, which is the first clue you get about the issue.  When you try and manually set the date through the VI-Client, you get a bunch of errors when you try and do anything and then the VI-Client froze.  The only option i found was to get that NTP server online.

Note: It may have been possible to do it via powershell or cli commands, however i had needed to get the NTP servers online anyway, and once this occurred, the ESXi servers re-synced and was able to respond.

Why the 2TB Limit in ESX 4.1

October 12, 2010 2 comments

So i was asked this question by a collegue of mine.  “Why is there still a 2TB size limit to a LUN in ESX”.   The argument was that in this day and age, and with ESX now running on a 64-bit kernel, why are we still ham-strung by this limitation?  After some consideration and thinking it was thought that maybe VMFS was the issue, but it can’t be because you can create extents and one big VMFS volume.

Well the answer is that ESX (& ESXi) are still using the SCSI-2 Standards. Yes the same SCSI-2 that was from ~1995.  The ultimate issue has to do with the way the standard addresses the “READ_CAPACITY” of the LUN.  It uses a 10-byte call for the capacity, which limits the return to a 32-bit number. (It actually is just under a 32-bit number, the last value of 0xffffffff is acutally reserved, and thus can’t be used.  This limits you to 2199023255040 bytes, which is just under the 2TB limit.

The only current work-around is extents, which are much less then ideal.

So until VMware decides to update their outdated storage methodology, we’re stuck with the 2TB limit.

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